AbstractIsotope excited energy‐dispersive X‐ray fluorescence determination of silver in photographic materials yields poor reproducibility because of difficulties in reproducing the geometry. By placing the film sample between the detector and the radioactive source this difficulty is overcome. The theory of such an arrangement indicates that effects due to varying thickness of film base or unequal coating in the case of double‐coated film play a minor role. The suggested improvements in measuring geometry should be of value for any application in which samples are in the form of thin foils or s